Siemens 3UG4 - Page 338

Accessories
13.2 Accessories for 3UG4 monitoring relays
3UG4 / 3RR2 monitoring relays
338 Manual, 05/2016, NEB927043002000/RS-AC/004
Transformer connection
Transformer connecting cables must be twisted and not routed in parallel to live cables to
protect from emitted interference. Keep the length of the connecting cables to a minimum.
The resistance at the transformer connecting cable must not exceed 5 Ω to ensure correct
fault current monitoring. This is ensured by the following limits given here as examples.
Conductor cross-section [mm²]
AWG/[kcmil]
Max. cable length [m]
0.5
20
70
1.0 18 140
1.5
16
210
2.5 14 / 12 300
4.0
1)
10
550
1)
only possible in the case of transformers with a 210 mm diameter
Note
We recommend using twisted cables.
①
Maximum cable lengths (see table above)
①
Length ≥ 10 m (shielded, twisted, grounded cables)
Note
Use shielded, twisted, and grounded
cables for transformer connecting cables with a length
of more than 10 m.